Generation of Alfvénic (magnetohydrodynamic) vortices by the interaction of compressible plasma
flows with magnetic field-aligned blunt
obstacles is modelled in terms of magnetohydrodynamics. It is found that periodic shedding of vortices with
opposite vorticity is a robust feature of the interaction in a broad range of plasma parameters: for plasma-beta from
0.025 to 0.5, and for the flow speeds from 0.1 to 0.99 of the fast magnetoacoustic
speed. The Strouhal number is the
dimensionless ratio of the blunt body diameter to the product of the period of vortex shedding and the inflow speed. It
is found to be consistently in the range
0.15-0.25 in the whole range of parameters.
The induced Alfvénic vortices are compressible and contain spiral-armed perturbations of the magnetic field strength and plasma mass density up to 50-60 % of the background values. The generated electric current also has
the spiral-armed structuring.

The influence of a few different Alfvén speed profiles V
m A(z) on the development of vertical
oscillations of a curved coronal slab is investigated.
Three particular cases are discussed: (a) {dV
m A}/{dz}<0,
(b) {dV
m A}/{dz}=0, (c) {dV
m A}/{dz}>0. These cases correspond respectively
to the presence of wave tunnelling into the ambient medium above the slab (a),
lack of any tunnelling (b), and tunnelling into the ambient medium below the slab (c).
Two-dimensional ideal magnetohydrodynamic equations are solved by numerical means and the slab oscillations
are triggered impulsively by an initial pule in the vertical component of the momentum.
We find that vertical oscillations exhibit time-signatures with characteristic wave period P and
attenuation time au. These parameters vary with V
m A(z).
A smallest value of P is associated with the case of (c).
A strongest attenuation (smallest au) of vertical oscillations takes place in the case of (a).
A simple model of coronal loop oscillations leads to numerical results which are akin to the observational data
of Wang & Solanki (2004).

Aims. We consider impulsively generated oscillations in a 2D model of a curved solar coronal arcade loop that consists of up to 5 strands of
dense plasma.
Methods. First we do a simulation for a loop which consists of two curved strands. We evaluate by means of numerical simulations an
influence of a distance between the strands and their number on wave period, attenuation time and amplitudes of standing kink waves.
Results. The results of the numerical simulations reveal that only strands which are very close to each other (distance comparable to the strand
width) considerably change the collective behavior of kink oscillations. More distant strands also exhibit some coupling of the oscillations.
However, their behavior can essentially be explained in terms of separate oscillating loops. We compare the numerical results with recent
TRACE observational findings, and find qualitative agreement.